A conventional headlight is adapted for use in a vehicle, and includes a shell, and a plurality of light emitting modules disposed in the shell. Each of the light emitting modules can independently emit a light beam. The light emitting modules cooperatively form a high beam or a low beam. The orientation of each of the light emitting modules may be required to be adjusted for emitting the light beam at an output angle that is satisfied with the regulations. However, since the light emitting modules are separately mounted in the shell, when a user needs to adjust light output angles of the light beams emitted from the light emitting modules, he or she has to adjust the light emitting modules one by one. In such a manner, the user requires to repeat such an orientation adjustment for many times, thus resulting in a time-consuming adjusting operation. In addition, since the orientations of the light emitting modules are individually adjusted, when the user adjusts the orientation of one of the light emitting modules, the orientation of an adjacent one of the light emitting modules which has been adjusted may be required to be re-adjusted. As a result, the adjusting operation becomes quite complicated.